In the winter, I preheat the water to 180 degrees before beginning my 54 mile commute and have the grill 100% blocked. When I EOC the heat in the block drops below 150 degrees. So even though the thermostat is allowing only a small amount of water to circulate through the radiator, it is enough to keep the water in the block below 150 degrees and limit the amount of time I can stay in lean burn.

On my car, when I bypass the radiator, I am able to regulate the water temp to stay above 180 degrees 100% of the commute and increase the lean burn time.

I have a temp sensor in both the top and bottom radiator hoses. During cold weather, with a 100% grill block and all of the water bypassing the radiator, I still see a 20 to 30 degree drop in the water temp from when it exits the top of the engine, goes through the bypass hose and re-enters the bottom of the engine.

When you add the time the engine is off and the water cools when I EOC, with out the bypass my lean burn time would be greatly reduced.

I'm not aware of any thermostat that will block 100% of the water exiting the block when the engine is running. It may be because the mechanical water pump needs some water flow at all times in order to work properly.

I did read that the super efficient VW XL1 uses an electric variable speed water pump that can be completely turned off when more engine heat is needed. Of course this is computer controlled.

I have mentioned before that one of my goals for maintaining lean burn in the Insight is to keep the water temp in the 180 to 190 degree range at all times. Even with a 100% blocked grill (manually adjustable) I was not able to meet this goal in winter, especially while using EOC for as much as 20% of the miles driven.

So I designed a system that uses a 3 way "T" valve to modulate the amount of coolant flowing through the radiator from 100 percent to as little as 0 percent that can be adjusted from inside the car.

For safety, I also have a digital temp sensor where the coolant exits the upper radiator hose and another where the coolant re-enters the engine in the lower radiator hose.

The 3 way valve never blocks the flow of coolant out of the engine, it just diverts as much as 100 percent of the flow around the radiator.

Here are some pictures

The T valve is attached in line with the upper radiator hose between the engine and radiator. The bypass hose attaches inline with the lower radiator hose between the radiator and the engine,

Attached to the T valve is a push-pull cable with 3 inches of "throw". This cable extends into the passenger side of the firewall.

Here is the valve being test fitted in the car.

Here is the in-car adjustment handle. It is the lowest cable with the long lever handle. Above it are the knobs for adjusting the warm air intake and the adjustable grill block detailed previously in this thread.

This system worked flawlessly all winter. One morning with an outside temp of18 degrees, I was able to make my 54 mile commute to the shop while diverting 100% of the coolant past the radiator. The highest water temp was 190 degrees.

i want to build the same setup because when i P&G i never build enough heat to be able to use heat in winter. And my warm up would be faster and my block heater setup would be more efficient. I think this rad bypass setup would work good with me because i dont have a thermostat with my electric water pump setup so there is allways coolant passing in my rad when the electric water pump turns

can you tell me where did you get the valve and fittings and cable and hardware ? and i could even send you money if you build me a valve setup with cable without the hoses

I agree, I think this rad by-pass would help you keep your water temp in a more efficient range in winter. You may even get better heat ups if you insulate the by-pass hose since water is constantly circulating thru the hose.

I got the 3 inch "throw" push pull cable and mounting hardware from JEGS. They have many lengths needed for our custom applications. The cable was about $50 and each of the mounting hardware for each end is $10 each.

All the other items I got from E-Bay.

The 1 inch stainless T valve is the most specific item needed. The ball inside this valve must have 3 holes in it which forms a T pattern thru the ball. Some other valves only have 2 holes which form an "L" pattern in the ball and will not work in this application. It cost about $50 and came from China.

All the mounting hardware for the valve is custom formed from .090 inch thick aluminum plate. and 2- 1 1/2" "U" clamps.

Because the mounting of this valve is such a "custom" application for your
vehicle, I would not be comfortable trying to do the fabrication unless I had access to your car. But I would be happy to try to answer any questions you my have. Thanks

I agree, I think this rad by-pass would help you keep your water temp in a more efficient range in winter. You may even get better heat ups if you insulate the by-pass hose since water is constantly circulating thru the hose.

I got the 3 inch "throw" push pull cable and mounting hardware from JEGS. They have many lengths needed for our custom applications. The cable was about $50 and each of the mounting hardware for each end is $10 each.

All the other items I got from E-Bay.

The 1 inch stainless T valve is the most specific item needed. The ball inside this valve must have 3 holes in it which forms a T pattern thru the ball. Some other valves only have 2 holes which form an "L" pattern in the ball and will not work in this application. It cost about $50 and came from China.

All the mounting hardware for the valve is custom formed from .090 inch thick aluminum plate. and 2- 1 1/2" "U" clamps.

Because the mounting of this valve is such a "custom" application for your
vehicle, I would not be comfortable trying to do the fabrication unless I had access to your car. But I would be happy to try to answer any questions you my have. Thanks

sorry for the thecnical question.
do you think that the valve can travel between the 2 positions in the picture with 3 inch of throw? because with the way i will be placing the valve
in my car this is the 2 positions i will need

but i cant find a barbed hose fitting that is 1 1/4 do you have a link where i can find them?

Francis, The 3 way valve appears to be just like the one I am using in the 1 inch size, so I am very confident you can make it work in your application.

On my car, the two ball positions shown in figure "3" are what I am using. The one on the left is when all the water is exiting the engine block and going to the radiator. The figure on the right is when the water from the block is diverted down the by-pass hose. The water is entering the valve from the left side in both figures. The ball valve handle only has to rotate 90 degrees to make this transition. The push pull cable cannot move the handle much more than 90 degrees.

On the two figures you circled, the handle would need to move 180 degrees, which would cause the cable to bind. My simple mind thinks by using both of the figure "3" positions and orienting the valve for your application, you can make the 90 degree handle movement work. The ball valve may be "upside down" with the handle also "upside down". I may be missing something here and just be focused on the solution that worked for me. So feel free to ignore what I have written above.

I was able to find 3 options for the 1.25 inch brass hose barbs on Amazon. Sorry I don't know how to post links, but the company names are as follows:

Man, any of these mods would possibly have meant a failure on the visual inspection portion of the California SMOG test I did today. You all have more fun than the Cali smog dance allows. (The price we pay for air that does not burn the eye and poison the lungs.)